Oxidation/Reduction

Oxidation/Reduction

• What is an oxidation reaction?

• Where electrons are lost

• What is a reduction reaction?

• Where electrons are gained

• What is happening in a Redox reaction?

• One substance loses an electron(s) and the other gains the electron(s)

Respiration• What is being oxidized in cellular respiration?

• Glucose, since it will lose electrons.

• What does glucose become once it is oxidized?

• Carbon dioxide

• What is being reduced?

• Oxygen, since ultimately it will gain the electrons?

• What does reduced oxygen become?

• Water

Oxidizing Agent• The oxidizing agent is the recipient of the

electrons and therefore is the agent responsible for the oxidation

• Why doesn’t the oxidation of glucose occur in one single step?– It would be too explosive and not enough

energy would be harnessed

• There are other oxidizing agents for respiration, besides oxygen.

What is the oxidizing agent here?

What is the oxidizing agent here?

NAD+

How is energy transferred?

• It is important to see that there is a change in the covalent status of electrons as they are transferred throughout respiration

• The electrons begin the journey in an unstable configuration and end in a stable molecule

Glycolysis

What does the hexokinase enzyme do?

Why would the cell invest ATP, when it is attempting to make more ATP’s?

What would the phosphofructokinase do?

So far how many ATP’s have been invested?

What does the dehydrogenase enzyme do?

What method is used here to generate ATP?

Removal of water rearranges substrate electrons and makes remaining P bond unstable

What does pyruvate kinase do?

The oxidizing agent of Glycolysis

• What is the oxidizing agent of glycolysis?

• NAD+

• Without NAD+ glycolysis cannot continue

• Is glycolysis anaerobic or aerobic?

• It is anaerobic, does not require oxygen.

Do MP3 tutor cell resp. part 1

9 minutes

Formation of Acetyl CoA

Total Energy Yield So Far:

• From Glycolysis:

• 2ATP’s and 2 NADH’s

• From Pyruvate - Acetyl CoA :

• 2 NADH’s

• From Krebs Cycle:

• 2 ATP’s, 6NADH’s, and 2 FADH2’s

• Where is all of the energy?

IT IS ALL LOCKED IN THE NADH’S AND THE FADH2’S!

So far the ATP’s have been generated via substrate level phosphorylation, now it’s time for chemiosmosis:

The Electron Transport Chain:

• What is the ETC? Where is it located?

• It is a series of electron carrier molecules, that transfer electrons to each other through a connected series of redox reactions.

• It is located within the inner membrane of the mitochondrion

What is the role of oxygen?

• The highly electronegative oxygen is the only molecule capable of receiving the stable electron from cytochrome a3.

• The cytochrome electron carriers are proteins with heme prosthetic group.

• The iron of the cytochromes transfers electrons

• DEMO

The Final Count• For every NADH produced in the mitochondrion,

how many ATP’s are created via oxidative phosphorylation?

• 3

• For every FADH2 produced, how many ATP’s are created via oxidative phosphorylation?

• 2• For the 2 NADH’s generated in glycolysis how

many ATP’s are created?• 2

• 2 NADH’s from glycolysis ---->

• 2 NADH’s from glycolysis ---->4-6 ATP’s

• 8 NADH’s from the mitochondrial matrix ---->

• 2 NADH’s from glycolysis ---->4-6 ATP’s

• 8 NADH’s from the mitochondrial matrix ----> 24 ATP’s

• 2 FADH2’s from KC ----->

• 2 NADH’s from glycolysis ----> 4-6 ATP’s

• 8 NADH’s from the mitochondrial matrix ----> 24 ATP’s

• 2 FADH2’s from KC -----> 4 ATP’s

• Total ATP’s from oxidative phosphorylation =

• 2 NADH’s from glycolysis ----> 4-6 ATP’s

• 8 NADH’s from the mitochondrial matrix ----> 24 ATP’s

• 2 FADH2’s from KC -----> 4 ATP’s

• Total ATP’s from oxidative phosphorylation = 32- 34 ATP’s

• ATP’s from substrate level phosphorylation =

• 2 NADH’s from glycolysis ---->4-6 ATP’s

• 8 NADH’s from the mitochondrial matrix ----> 24 ATP’s

• 2 FADH2’s from KC -----> 4 ATP’s

• Total ATP’s from oxidative phosphorylation = 32 ATP’s

• ATP’s from substrate level phosphorylation = 4

• GRAND TOTAL = 36- 38 ATP’s

Do MP3 tutor cell resp. part 2(12 minutes)

Efficiency of Respiration• The total G for the combustion of

glucose = -686 kcal/mol.

• Phsophorylation of ADP to ATP stores aproximately 7.3 kcal/mole

• Respiration efficiency is 7.3 x 38 = 277.4 kcal/mole

• 40% use of available energy is used

• A car can use only 25% of energy stored in gasoline

• Where does the rest of the energy go?

Variables in ATP yield:

• Some mitochondria differ in permeability to protons, which effects the proton motive force.

• Proton motive force may be directed to drive other cellular processes such as active transport.

• ATP yield is inflated by rounding up

• Prokaryotic cellular respiration is slightly higher since no mitochondrial membrane used to transport electrons from NADH.

Poisons:

• Rotenone blocks the first electron carrier, used to poison fish, and insects.

• Cyanide and carbon monoxide block cyt a3, so what will the symptoms be?

• Oligomycin - physically blocks the passage of H+ through ATP synthase. It is used on skin to combat fungal infections.

• Uncouplers such as dinitrophenol, makes membrane leaky to H+

How does glycolysis proceed in the absence of oxygen?

• What is the oxidizing agent of glycolysis?

• NAD+

• How is NAD+ regenerated so that glycolysis can continue?

• Through the ETC.

• How is NAD+ regenerated in the absence of ETC (no oxygen)?

Does metabolism slow (with aging) or do we?

• http://health.msn.com/fitness/articlepage.aspx?cp-documentid=100119089

• Both. But the slowing of metabolism is a real thing. “The primary thing that seems to occur is that mitochondria in the cells slow down with age,” says Newgard. (Think of mitochondria as little energy factories in cells that convert nutrients to power.)

And that’s not all. Barry Stein of Wake Forest University School of Medicine is writing a book about staying fit after 50. As he explains, “As we age, we are subject to sarcopenia—muscle wasting. Since muscle burns more energy than fat, this means the metabolic load goes down and metabolism reflects that.” That is, if you do nothing about your loss of muscle with age, it will take you longer to burn off a candy bar at age 60 than at 20.

• Add to this the fact that we tend to become less active as the years go by, and you can see why the inches start to gather around your waist.

How to slow the slowing • If you’re tempted to throw up your arms and give in to

the extra inches (who can argue with mitochondria?), think twice. There are things you can do to keep your metabolism efficient. Exercise is No. 1. “Exercise actually increases the number of mitochondria. And also increases their metabolic activity,” explains Newgard.

• Exercise also simply burns calories. Twins Tammy and Lyssie Lakotos, authors of Fire Up Your Metabolism, recommend both cardiovascular activity and weight training. “Cardiovascular activity burns calories while you do it. Additionally, you could burn about 20-30 additional calories afterwards, which may not seem like a big amount daily, but adds up over a lifetime,” says Tammy Lakotos. Strength training is effective long after you’ve put down the barbells because muscle burns more calories than fat while you’re at rest.